A complex set of variables affect metal detection and detection sensitivity. Some physical characteristics of metal objects that influence detection are material composition, shape, surface area, surface and internal electrical and magnetic properties, and finish. The orientation of a test object can greatly influence detection as can the direction and speed or changes in speed while passing through the detection zone. Nearby large metal objects and metal moving in near proximity to a metal detector also affect operation, as do temperature and humidity, and can be a cause for nuisance alarms. Additionally, most currently manufactured walk-through metal detectors have some means for programming the operation of the detector for special conditions or requirements; these variables and the effect they have on the operation of in-plant detectors must be considered if a test program is to be effective. This practice is intended to minimize the impact of these variables on the operation of in-plant detectors by systematically testing the installed detectors in the operating environment with the test object(s) specified by the regulatory authority requirements.

This practice may be used to determine the critical test object from a group of test objects, its critical orientation, and the critical test path through the detection zone. This information may allow the use of a single test object for setting the operational sensitivity of the detector and performing periodic performance evaluations necessary to ensure a high probability that all test objects in the group are detectible within the capabilities of the detector.

The detection sensitivity map(s) generated by this practice provides baseline metal detection data for the specified test objects and can serve as a foundation for in-plant walk-through metal detector set-up and performance evaluation testing. The detection sensitivity map(s) may be incorporated into a detector performance test log in support of performance evaluation practices.

This practice may provide insight into certain metal detection characteristics of walk-through metal detectors, particularly the effect of different metals and test object orientations on detection capability, that are useful for optimizing detector sensitivity settings for detection of specified weapons or shielding material, or both.

Periodic performance of this practice and analysis of the results may provide a means to monitor the state of health of in-plant detectors and to gain further insight into detector application and operation.

1. Scope

1.1 This standard practice covers a procedure for determining the weakest detection path through the portal aperture and the worst-case orthogonal orientation of metallic test objects. It results in detection sensitivity maps, which model the detection zone in terms related to detection sensitivity and identify the weakest detection paths. Detection sensitivity maps support sensitivity adjustment and performance evaluation procedures (see Practices C1269 and C1309).

Note 1—Unsymmetrical metal objects possessing a primary longitudinal component, such as handguns and knives, usually have one particular orientation that produces the weakest detection signal. The orientation and the path through the detector aperture where the weakest response is produced may not be the same for all test objects, even those with very similar appearance.

Note 2—In the case of multiple specified test objects or for test objects that are orientation sensitive, it may be necessary to map each object several times to determine the worst-case test object or orientation, or both.

1.2 This practice is one of several developed to assist operators of walk-through metal detectors with meeting the metal detection performance requirements of the responsible regulatory authority. (See Appendix X2)

1.3 This practice is neither intended to set performance levels, nor limit or constrain operational technologies.

1.4 This practice does not address safety or operational issues associated with the use of walk-through metal detectors.

1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.